This invention relates to an electrode which is positionable in contact or proximity with a specified portion of an article which is being transported.
Plate-like, or lattice- or rake-shaped electrodes are usually used when there is a need to bring a specified portion of an article into contact with an electrode during the transport of the article, for example, when sealed containers made of electrically insulating material such as plastics or glass and having a parenteral solution, retorted food or like contents enclosed therein are checked for pinholes, cracks, etc. (hereinafter referred to collectively as "pinholes") by positioning the container between a pair of electrodes, impressing a voltage across the electrodes to produce a discharge current on the container and detecting the discharge current.
With reference to FIG. 5, such a plate-like, or lattice- or rake-shaped electrode Y has resiliency and is so arranged as to at least partially position in the path of transport of an article X, such that the article X in transport moves forward in contact with the electrode Y while pushing the electrode away against the resiliency of the electrode.
However, when the article X moves some distance, the electrode Y, with its restoring force, returns to its original vertical position out of contact with the article, with the result that the electrode fails to fully contact or gain access to a portion X' shown in FIG. 5 although the article has a simple shape. This tendency becomes more pronounced when the article has a complicated shape. Thus the electrode is not always capable of fully contacting or gaining access to the whole desired portion of the article whether continuously or simultaneously. Furthermore the electrode is subject to fatigue due to contact, friction or bending and therefore is not durable. When having a complicated shape or recess at the specified portion, the article involves a dead zone where the electrode is unable to contact or gain full access to the article. The conventional electrode has another drawback in that it is likely to mar and deteriorate the article if the article is made of soft plastics or like material.
When the electrode is used for checking sealed containers for pinholes by the above-mentioned method, the drawback of the electrode that it is incapable of fully contacting or gaining access to some desired portion of the container reduces the accuracy of checking. For example, if the article X shown in FIG. 5 has a pinhole at the portion X', the electrode is unable to contact or gain full access to the defective portion, failing to produce a discharge current sufficient for detecting the pinhole. Reduced checking accuracy similarly results from the drawback involving a dead zone.
The main object of this invention is to provide an electrode free of the foregoing problems.